This invention relates generally to a drive system for a machine; and more specifically to an index drive system for a molding machine; and still more specifically to an index drive module employing a servomotor-driven turret, preferably for use in moving molding elements, such as core rods, into different operating stations of the molding machine.
In prior art molding machines, such as injection-blow molding machines, a turret carrying core rods or other machine elements is mounted to a supporting frame or table for both axial and rotational movement relative to the frame or table. In a representative prior art injection-blow molding machine a plurality of core rods carried by the turret are first positioned within multiple cavities of an injection mold in an injection molding station. In this station extruded plastic material is injected into the mold cavities, to thereby form a parison on each of the core rods. Thereafter, the multi-cavity mold in the injection molding station, as well as a multi-cavity mold in a downstream blow molding station are opened, and the turret is rotated to direct the core rods with the parisons thereon into the blow molding station. In order to accomplish this function, it is necessary to first axially lift or raise the turret, to thereby move the core rods into an uninterrupted free space between the mold sections of the open, multi-cavity injection mold, and thereafter index the turret, while it is in its raised position, to move the core rods into an uninterrupted free space between the mold sections of the open, multi-cavity blow mold in the blow molding station. Thereafter the blow mold is closed, and the turret is axially lowered to position the core rods with the parisons thereon into the proper position within the cavities of the closed blow mold. Then pressurized gas is directed into the parisons through openings in the periphery of the core rods, to expand each of the parisons into engagement with the surfaces of a corresponding mold cavity, and thereby form each parison into the desired shape of the article to be molded.
After the product has been molded into its desired shape in the blow molding station, the multi-cavity blow mold is opened, the turret carrying the completed articles is then raised into the uninterrupted free space between the mold sections of the open blow mold, and the turret is again indexed to a final stripping station, at which the completed product is cooled and removed from the core rods for subsequent packaging.
From the above description, it should be apparent that the turret carrying the core rods needs to be axially moveable both to properly position the core rods within the closed injection and blow molds during the respective injection and blow molding operations, and to properly position the core rods into the uninterrupted free space between the open mold sections of the injection and blow molds, to permit the core rods to be indexed between stations. Moreover, to index the core rods between stations, the turret also needs to be capable of being rotatably indexed.
In prior art molding machines it is a difficult and time-consuming operation to assemble and properly align the turret and its associated drive elements. For example, in a number of prior art systems it is quite difficult and time consuming to align the various components of the turret system so that the axially moveable and rotatable shaft carrying the turret is precisely aligned with the rotary drive unit, e.g., a Ferguson Indexing Unit, generally located in a position remote from the turret.
Representative prior art molding machines employing rotatable turrets are disclosed in U.S. Pat. Nos. 3,881,854, issued to Rainville; 3,887,316, issued to Hestehave; 4,162,879, issued to Makowski; 4,540,543, issued to Thomas, et al.; 4,604,258, issued to Valyi; 4,801,260, issued to Oles, et al.; 4, 941,815, issued to Julian; 4,941,816, issued to Aoki, et al. and 4,946,367, issued to Nakamura.
U.S. Pat. No. 4,540,359 issued to Yamazaki, discloses an injection molding machine wherein a servomotor is employed to assist in controlling the operation of both a clamping mechanism and a plastics injection feed system. In particular, the device disclosed in the Yamazaki '359 patent includes transmission shafts 30 and 31, which are associated to be moved toward and away from each other through a clutch mechanism 32, and wherein a joint 33 is connected to the outer end of the clutch shaft 32B for connection to transmission shaft 30. The joint 33 and transmission shaft 30 are connected to a spline or key 34 forming part of the transmission shaft 30, to thereby permit relative axial movement between the shafts 30 and 31, while permitting joint rotational movement of these shafts by servomotor 40.
It should be apparent that the Yamazaki '359 patent does not disclose or relate in any way to a drive module employing an axially and rotatably moveable turret, wherein the rotational movement imparted to the turret is controlled by a motor.